Absorption refrigeration machine



July 14, 1970 FIG. I

L. A. M NEELY ABSORPTION REFRIGERATION MACHINE Filed June 7, 1968 LI'LJAVLQ II "I, I I l l L N 9 o' u g E INVENTOR. LOWELL A. MC NEELY.

ATTORNEY.

United States Patent O 3,520,150 ABSORPTION REFRIGERATION MACHINE Lowell A. McNeely, Indianapolis, Ind., assignor to Carrier Corporation, Syracuse, 'N.Y., a corporation of Delaware Filed June 7, 1968, Ser. No. 735,327 Int. Cl. F25b 43/04 US. Cl. 62-475 3 Claims ABSTRACT OF THE DISCLOSURE An absorption refrigeration machine having a generator and a condenser on the high side thereof and an evaporator and absorber on the low side employing a pump having an inlet tank associated therewith to transfer solution from the low side to the high side of the machine.

BACKGROUND OF THE INVENTION In a two-pressure absorption refrigeration machine employing a pump to transfer solution from the low side to the high side of the machine, numerous problems are encountered. Ordinarily, solution to be pumped is supplied to the pump from the absorber. At start-up, there may be a period of operation during which solution is not supplied to the pump. The operation of the pump without solution flowing therethrough can cause overheating and damage thereto. While the machine is operating, the pump is supplied with slugs of liquid from the absorber rather than a steady flow. This can cause undesirable, fluctuating pump noise.

A third problem that is encountered is the transfer of noncondensible gases created by chemical reaction in the machine. It is desirable to collect and store these gases on the high pressure side of the machine due to the smaller storage space required when the gas is under pressure. It is therefore necessary to pump these gases to the high side of the machine along with the solution.

SUMMARY OF THE INVENTION This invention relates to an absorption refrigeration machine employing a pump to transfer solution and nonoondensible gases to the high pressure side of the machine. A pump inlet tank is provided communicating with the pump through three openings to prevent dry running of the pump at start-up, slugging of the pump due to the variable flow of solution supplied from the absorber, and to provide for passage of noncondensible gases through the pump.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic flow diagram of an absorption refrigeration machine; and

FIG. 2 is a sectional view of the pump inlet tank employed in the absorption refrigeration machine of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 of the drawing, there is shown a refrigeration system comprising a primary absorber 10, a condenser 11, an evaporator or chiller 12, a generator 13, a solution-cooled absorber 14 and a liquid-suction heat exchanger 15 connected to provide refrigeration. A pump 16 is employed to circulate weak absorbent solution from primary absorber to generator 13. As used herein the term weak absorbent solution refers to a solution which is weak in absorbent power and the term strong absorbent solution refers to a solution which is strong in absorbent power. A suitable absorbent solution for use in the system described is water and a suitable refrigerant is ammonia.

3,520,150 Patented July 14, 1970 Liquid refrigerant condensed in condenser 11 passes through refrigerant liquid passage 18, and refrigerant restriction 20 to heat exchange tube 22 of liquid-suction heat exchanger 15. The liquid refrigerant is cooled in tube 22 and emerges from the liquid-suction heat exchanger and passes through refrigerant restriction 24 into heat exchanger 26 in chiller 12.

A fluid medium such as water to be chilled passes over the exterior of heat exchanger 26 where it is chilled by giving up heat to evaporate refrigerant within the heat exchanger. The chilled medium passes out of the chiller 12 through line 28 to suitable remote heat exchangers (not shown) after which it is returned to the chiller through inlet 30 for rechilling.

The cold refrigerant evaporated in heat exchanger 26 passes through refrigerant vapor passage 32 and through liquid-suction heat exchanger 15 in heat exchange relation with liquid refrigerant passing through tube 22. The refrigerant vapor then passes through refrigerant vapor passage 34 into solution-cooled absorber 14.

The solution-cooled absorber 14 is formed within a tubular or cylindrical vessel 38 by a tubular, preferably, cylindrical internal baffle 36 which divides the tubular cylindrical vessel 38 into the solution-cooled absorber 14 and a second solution chamber 40. Vessel 38 is preferably closed at both ends. Baffle 36 may be provided with a top cover plate 37 having a plurality of vapor discharge apertures 42 therein to allow vapor to escape from solutioncooled absorber 14 into chamber 40.

A weak solution heat exchanger 44, preferably comprising a helical coil is disposed within solution-cooled absorber 14. A plurality of horizontal plates 46 are secured to a central support 48 and arranged within balfie 36 to cooperate with annular grooves 50 and heat exchanger 44 to provide a tortuous path for passage of vapor and solution through solution-cooled absorber 14. Suitable packing such as Raschig rings 52 may fill the space between the uppermost plate 46 and the top of the solution-cooled absorber to reduce the tendency for solution froth to escape through discharge apertures 42.

A refrigerant vapor distributor header 54 is secured to close the bottom of bafile 36. Header 54 is provided with refrigerant vapor ports 56 for passage of refrigerant vapor from line 34 into solution-cooled absorber 14 and chamber 40. Strong solution from generator 13 is supplied to the top portion of solution-cooled absorber 14 through line 58. The strong solution passes downwardly through the solution-cooled absorber in counterflow re lation to upwardly passing refrigerant vapor and weak solution passing through coil 44. A strong solution discharge passage 60 is provided adjacent the lower portion of bafile 36 for passage of solution from the solutioncooled absorber into chamber 40.

Solution discharge passages 62 are provided for passing a mixture of refrigerant vapor and solution from chamber 40 to primary absorber 10. Each of the discharge passages comprises a tubular member having an upper open end for admission of vapor and a solution inlet aperture 64 which is disposed below the level of absorbent solution in chamber 40. This insures a mixed flow of liquid and vapor to the primary absorber.

A cooling medium, preferably ambient air, is passed through the primary absorber 10 in heat exchange relation with the absorbent solution to cool the absorbent solution to promote the absorption of the refrigerant vapor in the absorber. The same cooling medium may be supplied to condenser 11 in heat exchange relation with refrigerant therein to condense the refrigerant.

Cold weak absorbent solution passes from primary absorber 10 through line 66 into pump inlet tank 68. Weak solution from inlet tank 68 is supplied to weak solution pump 16 through line 72. Liquid from pump 16 passes through pump discharge tank 74 to a rectifier heat exchange coil 76. From coil 76, the weak solution passes through line 78 to weak solution heat exchanger 44 in solution-cooled absorber 14. The weak solution from coil 44 passes through line 80 into the upper portion of generator 13 along with any vapor formed in coil 44.

Generator 13 comprises a shell 82 having fins 84 suitably afiixed thereto as by welding. The generator is heated by a gas burner 86 or other suitable heating means. The Weak solution is boiled in generator 13 to concentrate the solution, thereby forming a strong solution and refrigerant vapor. I

The hot strong absorbent solution passes upwardly through the analyzer section of generator 13 through analyzer coil 88 in heat exchange with weak solution passing downwardly over the coil. The Warm strong solution then passes through line 58 which has solution restrictor 87 therein and is discharged into the upper portion of solution-cooled absorber 14.

Refrigerant vapor formed in generator 13 passes upwardly through the analyzer section thereof where it is concentrated by mass heat transfer with weak solution passing downwardly over analyzer coil 88. Analyzer plates 90 in generator 13 provide a tortuous path for flow of solution and vapor to assure intimate contact therebetween to improve the mass heat transfer. The refrigerant vapor from the analyzer section passes through reflux plate 92 in heat exchange relation with absorbent condensed in rectifier 94. The vapor then passes through rectifier 94 in heat exchange relation with rectifier heat exchange coil 76. Absorbent condensed in rectifier 94 flows downwardly onto plate 92 Where it is heated by the refrigerant vapor passing therethrough. The heated absorbent is then passed to the generator along with the weak solution discharged into the generator from line 80. Refrigerant vapor passes from rectifier 94 through line 96 to condenser 11 to complete the refrigeration cycle.

Referring to FIG. 2, inlet tank 68 comprises a central cylindrical section 101 having a top section 103 and a bottom section 105; an inlet line 66, and a bleed valve 107 are provided in top section 103. Inlet line 66 communicates with absorber 10 to provide solution from the absorber to the inlet tank. A suitable screen 109 is provided around discharge line 72 to prevent scale and other impurities from passing through line 72 to the pump 16. Line 72 is provided with a first relatively small orifice 111 and a second orifice 113 substantially larger than orifice 111. The upper end of line 72 provides a third opening into line 72.

Under normal operating conditions, the absorber may provide slugs of solution through line 66- to inlet tank 68. Solution level in the tank therefore varies to some extent. The top of line 72 and upper orifice 113 are located such that under normal operating conditions the solution level in the tank will not reach the top of line 72 and not fall below orifice 113. Solution therefore flows through orifices 113 and 111 to pump 16. Since orifices 113 and 111 are normally both submerged the supply of solution to the pump remains relatively constant irrespective of the level in tank 68 resulting from the variable supply of solution to the tank. The flow of solution through line 72 from orifices 113 and 111 will induce fiow of noncondensible gases collected in the top portion of tank 68 through the open upper end of line 72 for transfer with the solution to the high pressure side of the system.

At start-up there may be a short period of time during which solution will not be supplied to tank 68 from the absorber. Solution level in tank 68 will drop rapidly 4 below orifice 113 which, in the absence of orifice 111, would prevent flow of solution to the pump and allow heat of the pump which is normally carried away by sub-cooled solution to vaporize solution and thus vapor bind the pump until a hydrostatic head sufiicient to force solution into inlet line is built up.

When this hydrostatic head is established, pumping again starts and in the absence of orifice 111 would be pumped rapidly until the level again dropped below 113. Orifice 111 therefore is provided to assure a supply of liquid to the pump at start-up. Orifice 111 is sized to pass a minimum quantity of solution to the pump thereby preventing complete drainage of tank 68.

While the described embodiment illustrates an orifice 111 which is substantially smaller than upper orifice 113, it is to be understood that this orifice could be the same size as orifice 113 if desired as the amount of liquid supplied to the pump when the liquid level in the tank is below orifice 113 would be less than the supply of liquid provided to the tank through both orifices when the liquid level is above orifice 113. Further a number of orifices could be provided on line 72 so that as the liquid level in tank 68 dropped the quantity of liquid supplied to the pump would decrease. Irrespective of the arrangement it is desirable to provide a decreased flow of refrigerant to the pump when the liquid level is below normal to prevent rapid drainage of the tank and the possibility of operating the pump with no solution therein.

While I have described a preferred embodiment of my invention it is to be understood that the invention is not limited thereto but may be otherwise embodied within the scope of the following claims.

What is claimed is:

1. An absorption refrigeration system comprising:

a generator;

a condenser, said generator and condenser being disposed on the high side of the system;

an evaporator;

an absorber, said evaporator and absorber being disposed on the low side of the system;

a pump for transferring solution from the low side of the system to the high side of the system;

a pump inlet tank; and

a discharge line projecting upwardly from the bottom of said tank, said line having an opening therein above the normal level of solution in said tank for passing noncondensible gases from said tank to said pump, said line having a first orifice therein disposed near the bottom of said tank for passing solution from said tank to said pump and a second orifice for passing liquid to said pump from a location above said first orifice and below said opening.

2. An absorption refrigeration system according to claim 1, wherein said first orifice is adapted to pass less solution than said second orifice.

3. An absorption refrigeration system according to claim 2 including a cylindrical strainer disposed about said line to retard flow of impurities into said line which may serve to close said orifices.

References Cited UNITED STATES PATENTS 3,357,203 12/1967 Briggs 62489 LLOYD L. KING, Primary Examiner U.S. Cl. X.R. 62-476, 489 

